This invention relates to loading dock shelters. In particular, it is directed to a deformable resilient seal for such a shelter.
Trucks or trailers are generally backed into a loading dock having a building doorway for purposes of loading and unloading the vehicle. A standard width of the building doorway matches the width of the truck body. In practice, a loading dock shelter is placed around the doorway to provide a weather seal during loading and unloading operations. These shelters typically provide a seal engagement between the dock structure and the truck.
One type of shelter employs a number of resilient dock seals of the pad type located on the sides and the top of the building doorway. Those members are formed of a compressible body of square, rectangular or trapezoidal cross section. One cross section is the so called L-pad configuration illustrated in U.S. Pat. No. 4,213,279. This L-pad seal has a series of distinct flange straps which are mounted together to engage the sides of the truck. By repetitive truck movement into and away from the dock such L-shape pads generally fail over time such that a good sealing engagement with the sides of the truck cannot be attained. One reason is the two piece foam construction of the unit.
As set forth in the '279 patent, the truck engages the compressible body so the dock seal must be located so that it overlaps or extends into the truck's path.
Various techniques have used variations of the L-pad structure in order to overcome these deficiencies. Typical are the reinforced L-pad designs in U.S. Pat. Nos. 4,601,142 and 4,718,207. These devices offer a further degree of complexity and cost. Additionally, such pads require a large force exerted by the truck in which to provide the sealing contact between the seal and the truck side. Given the fact that loading and unloading operations can occur in a variety of environmental conditions, with extremes of temperature, wind and rain, the compression and expansion characteristics of such dock seal members are compromised. Over time, the sealing engagement between the truck and dock seal is compromised.
To overcome these disadvantages in the prior art, other geometries have been proposed. One such geometry is found in U.S Pat. No. 4,574,542 where the truck backs against the outward protruding surface and causes a particular mode of inward deformation at the corner of the truck.
A modification of this configuration is shown in U.S. Pat. No. 4,799,341 by having the truck strike the outer projecting face of each of the side pads so that those pads flex or bulge outwardly so that the reduction in the opening in the back of the truck is minimized.
The difficulty with these techniques is that the truck directly strikes the nearly rigid outer face of the resilient pad at a corner thereof. The truck typically has flanges, hinge points, latches, and the like such that such contact can damage the pad and its outer waterproof cover. Further, the pad remains in the deformed condition so long as truck loading and unloading operations occur. Over time the shape of the pad tends to deform. More importantly, while in the compressed condition, the truck is not perfectly stable. That is, as forklift trucks enter and leave the truck the truck tends to "float" up-and-down as a function of its overall loading and shift from side-to-side as a result of uneven weight distribution as the forklift truck moves. This causes relative movement between the truck corner and the resilient pad increasing the propensity for damage.